Things That I Posesss: Raccoon Skull (Procyon lotor)

Procyon lotor skull, adult.

Raccoons are one of my absolute favorite American mammals. They’re not just charismatic, as seen by their omnipresence in North American folklore, but also very intelligent (I’ve learned this the hard way), yet people seem not to be very interested in them whether because they’re viewed as pests or because their small size and nocturnal tendencies mean encounters aren’t frequent for most people.

Therefore, I’m pretty pleased that my most complete mammal skull is from an adult raccoon, sex unknown, as there’s no smoking gun trait to determine sex from a raccoon skull (Ritke 1990).

Procyon lotor, anterior
The sinuses are for the most part, beautifully intact.

Procyon lotor, superior

Procyon lotor, inferior
Left tympanic bullae is partially missing, left ptyerygoid process a bit bent.

Upon writing this post, I realized that I didn’t have quite the best grasp of where procyonids fit into the larger carnivoran picture. The most recent molecular results that I know of place them as sister to mustelidae (Sato et. al 2012), but in the past they’ve been hypothesized to group with skunks (Mephitidae) and of course red pandas (Aliuridae), which now appear to be the successive outgroups to the Procyonid + Mustelid clade (Sato et. al 2012). Interrelationships within procyonidae are less clear, and genomic and morphological trees give conflicting results – what a surprise. While morphological data groups Procyon with Nasua, the coatis, with very strong support, equally strong signal from molecular data groups them with Bassaricus, the ringtail. This is one of those beautiful little conundrums that pop up everywhere when you get down to species and genus-level systematics, and I’m planning to keep an eye on it in the future.

Skull and mandible, left view. The tip of the left coronoid process is broken off.
Skull and mandible, left view. The tip of the left coronoid process is broken off.

Within Procyon lotor, there seem to be about twentyish subspecies, and if the font of human knowledge is to be trusted, my raccoon is most likely a representative of P. lotor hirtus, the Upper Missisippi valley raccoon, given that it was found near the Illinois-Wisconsin border towards its Easternmost extent.

As I mentioned, the skull is very, very complete, with just a few of the more fragile bones bearing damage. While this makes it quite nice to look at, it’s not interesting in the same way a roughed-up juvenile deer skull is, and I know next to nothing about the animal itself. The preparation of the skull was equally perplexing; it was found in basically perfect condition, with a few grass stains and skin folds still hanging onto it, but otherwise ready to pick up and take home. all I did to it was a light soak and peroxide bath, followed by a scrubbing and coating of glue to seal up the bones. This afforded me the opportunity to take some pictures of the skull with its teeth removed (I’m only missing the first pair of incisors and the L2 incisor).

Procyon lotor skull, teeth removed
Procyon lotor skull, teeth removed

If skeleton prep was always this easy, everyone would do it.

Procyon lotor skull, right side.
Procyon lotor skull, right side.

One of my goals with his blog is to make available to the internet at large a greater number of good-quality photos of skulls, bones, etc. So many posts are going to end up similar to this one, relatively light on content but heavy on high-resolution original photos, and in the near future, illustrations.  Towards that end, here are more pictures of the skull.

Procyon lotor skull, anterior
Guitar picks make for an excellent support structure when you need to elevate things ever so slightly. View of the basicoccipital.

Procyon lotor skullProcyon lotor skullProcyon lotor mandibleProcyon lotor skull


Refs.

Koepfli, K., Gompper, M., Eizirik, E., Ho, C., Linden, L., Maldonado, J., & Wayne, R. (2006). Phylogeny of the Procyonidae (Mammalia: Carnivora): Molecules, morphology and the Great American Interchange. Molecular Phylogenetics and Evolution, 1076-1095.

Ritke, Mark E. 1990. “Sexual Dimorphism in the Raccoon (Procyon Lotor): Morphological Evidence for Intrasexual Selection.” American Midland Naturalist: Vol. 124, No. 2, pp. 342-351

Sato, J. J., Hosoda, T., Wolsan, M. & Suzuki, H. 2004. Molecular phylogeny of arctoids (Mammalia: Carnivora) with emphasis on phylogenetic and taxonomic positions of ferret-badgers and skunks. Zoological Science 21, 111-118.

Sato, J. J., Wolsan, M., Prevosti, F. J., D’Elía, G., Begg, C., Hosoda, T., Campbell, K. L. & Suzuki, H. 2012. Evolutionary and biogeographic history of weasel-like carnivorans (Musteloidea). Molecular Phylogenetics and Evolution 63, 745-757.

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